1. Field of the Invention
The present invention relates generally to apparatus and method for controlling coating thicknesses applied to workpieces and, more particularly, an apparatus and method of operation therefor which will produce an essentially uniform and desired coating thickness across the width of a continuously moving and continuously coated strip-like workpiece regardless of strip thickness, width, camber, and velocity.
2. Description of the Prior Art
In the manufacture of elongated relatively thin, strip-like workpieces such as steel sheet or strip, and the like, the occurrence of a certain degree of camber in the strip across its width is virtually unavoidable. Furthermore, for a multitude of reasons, workpieces such as steel strip are commonly provided with coating before the strip is coiled into a final product.
Coating thickness of galvanizing material, paint, and other materials, on steel or other metal strip production lines is commonly controlled by a device known as an air knife which generally consists of an apparatus which directs an elongated thin pressurized gas jet, typically in the form of air or steam, across the width of the strip in order to control the thickness of coating material which has been freshly deposited on the strip, such as, for example, in an adjacent coating bath or galvanizing pot.
During coating or galvanizing, the strip usually passes under a roll positioned within the bath and then runs vertically upwardly to an upper roll. The air knife is typically located between these rolls and generally adjacent to the coating pot for directing any excess coating back into the pot.
In the usual arrangement, the coating thickness resulting from treatment of the strip by the air knife is then measured by a device above or "downstream" of the air knife. This device operates to transmit signals to the flow control mechanism of the air knife to increase or decrease the pressure of the air or steam in order to maintain a desired and preferably uniform thickness of coating on the strip. In addition to pressure changes, the position of the knife may also be varied.
However, as noted hereinabove, the strip being coated tends to not remain flat as it passes the air knife and usually cambers in a relatively random manner, thereby causing variations in coating thickness across the width of the strip from one to the other longitudinal side edge thereof or, more generally, from the center of the strip to each longitudinal side edge.
An advantage exists, therefore, for an apparatus and method of operation therefor which will provide an essentially uniform and desired coating thickness across the width of a continuously moving and continuously coated strip-like workpiece regardless of strip thickness, width, camber, and velocity.
It is therefore an object of the present invention to provide an apparatus which will produce an essentially uniform and desired coating thickness across the width of a continuously moving and continuously coated strip-like workpiece regardless of strip thickness, width, camber, and velocity.
It is a further object of the present invention to provide a method for producing an essentially uniform and desired coating thickness across the width of a continuously moving and continuously coated strip-like workpiece regardless of strip thickness, width, camber, and velocity.
Still other objects and advantages will apparent in light of the attached drawings and written description of the invention presented herebelow.